The present invention relates to scale treatment and eradicating bacteria in water supply systems, and, in particular, to an efficient treatment of scale and eradicating bacteria in water systems, in general, and Legionella pneumophila, in particular.
Various systems for preventing scale crystallization and precipitation in cooling towers and in hot and cold water systems have been installed in or outside the systems. Substantially, these systems prevent the crystallization and precipitation of scale by leaving the scale substances as suspended colloids.
For generations, many scale systems and devices have been invented and used by those skilled in the art. Among these systems are the modern and efficient systems based on the “Guldager” electrolytic method.
In these systems, aluminum (or magnesium) anodes, connected to an external electrical supply source, are immersed in metallic water tanks. The water becomes alkaline with high pH values close to the wall of the tank. As a result, calcium carbonate (CaCO3) precipitates and the aluminum anodes dissolve in the water as aluminum hydroxide—Al(OH)3.
These prior art systems prevent, to some extent, the formation of scale, leaving the precipitate as suspended colloids and coagulants without disposing of these colloids.
A more advanced prior art system, described in Israeli Patent No. 120003 to Elgressy, is a modified “Gulager” system but with non dissolving electrodes made of, or coated with, TiNiO. This system, which will be further described hereinbelow, disposes of the scale colloids.
It is also known that water may contain many kinds of bacteria that can be dangerous to animals and human beings. Especially dangerous is Legionella pneumophila, which can be fatal and cause painful death, particularly to smokers and alcoholics, and to patients suffering from problems in the immune system, such as patients having steroids prescriptions, patients after transplanting of organs, AIDS patients, etc.
Hence, drinking water must be disinfected against harmful bacteria, in general, and Legionella pneumophila, in particular.
Water disinfection, according to the teaching of the prior art, includes treatment of the water with sodium hypochlorite (NaClO). Since sodium hypochlorite above the concentration of 0.5 ppm is toxic and harmful to human beings, water disinfection with this substance is prohibited in systems of drinking water. Occasional warming of water to 70° C. is also regarded as an alternative treatment against the Legionella pneumophila bacteria. However, the Legionella pneumophila bacteria undergo various mutations at high temperatures, making the bacteria substantially immune to high temperatures. Additionally, various metal systems, particularly galvanized systems, suffer from increased corrosion at such elevated temperatures.
To date, there is no known treatment system that combines scale removal and water disinfection.
There is therefore a recognized need for, and it would be highly advantageous to have, a method of, and a system for treating water electrochemically, and disinfecting it from bacteria, and more particularly, from Legionella pneumophila. 